Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Stock-Based Compensation - Performance Based Stock Award (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 06, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-Based Compensation
Stock- based stock awards expense		$ 7,225	$ 2,996	$ 20,983	$ 7,121
Performance Based Stock Award
Stock-Based Compensation
Granted (in shares)	50,000			25,000
Weighted average grant-date fair value (in dollars per share)	$ 61.85
Stock- based stock awards expense		339		$ 1,653
Unrecognized compensation expense (in dollars)		$ 55		$ 55